As is known from the prior art, a radial tire has areas called beads designed to cooperate with the seats and flanges of a mounting rim, the said beads comprising a reinforcement structure in the circumferential direction, to which the carcass reinforcement is anchored. Radially on the outside of the carcass reinforcement is arranged a crown reinforcement comprising at least two plies whose role, among others, is to hoop around the said carcass reinforcement when the tire is being pressurized for use above the said beads. Radially outside the crown reinforcement is positioned a tread with a plurality of reliefs that form the pattern of the tire. Between each bead and each axial end of the crown extends a sidewall of the tire whose function is to provide a mechanical link between the said bead and the said crown while undergoing more or less pronounced bending during rolling.
This bending leads to substantial deformations associated with the marked variations of the sidewall curvature and when a tire is used on rough ground with numerous bumps or obstacles, the combination of forces can give rise to breaking of the sidewall rubber or even damage to the carcass reinforcement. To overcome this problem it has been proposed to add to the tire sidewalls at least one ply of rubber reinforced with cables, the said cables making a non-zero angle with the radial or meridian direction. Document U.S. Pat. No. 3,464,477 proposes to add within each sidewall and on the inside of the carcass reinforcement a reinforcement extending on either side of the half-way height of the sidewall and over a fraction of the radial height of the said sidewall. This solution, however, which is very effective, has a disadvantage related to the fact that having regard to the radial heights of sidewalls, it is often difficult to obtain in the tire the desired angle of the reinforcements, let alone that the said reinforcements are subjected to stresses that have an adverse effect on their mechanical resistance even on account of the variable curvatures they undergo in the tire due to the sidewall deformations.
Document U.S. Pat. No. 5,078,192 describes a tire structure comprising in its sidewalls at least one supplementary reinforcement armature designed to protect the said sidewalls against aggressions during rolling, this reinforcement being formed by the winding in the circumferential direction of strips that comprise reinforcing elements orientated circumferentially; in the said document the strips are arranged edge to edge in a meridian direction. This solution raises many manufacturing problems since it requires the reinforcements orientated circumferentially to be positioned on a tire blank that has already been shaped.
Consequently, there is need for a solution that enables the reinforcement of tires intended to roll over difficult ground, but one which does not have the disadvantages of the technical solutions of the prior art mentioned above, and in particular one which makes it possible to shape the tire in the form of a toric blank produced on a building drum.
U.S. Pat. No. 4,438,796 describes a tire structure for carrying heavy loads (in particular, for use on civil engineering vehicles), in which at least one of the sidewalls has a supplementary reinforcement consisting of one or more layers comprising inclined reinforcements; in one variant, it is specified that each layer comprises a plurality of circumferential strips separate from one another within the same layer.